JP2011-202458A discloses a hybrid construction machine including a variable capacity main pump that drives an actuator by discharging working oil, a sub pump that discharges working oil in order to assist an output of the main pump, a regenerative motor that rotates in order to perform regeneration upon reception of a working oil pressure, and a rotating electric machine driven by the regenerative motor. In this type of hybrid construction machine, the working oil discharged from the main pump is throttled by a throttle on a downstream side of a control valve, and a tilt angle of a swash plate of the main pump or the like is controlled (negatively controlled) in accordance with a working oil pressure (a pilot pressure) on an upstream side of the throttle.